Valve stem seals are used in OHV engines to prevent oil pressure fed to rockerarms/cams from running down the valve stems and into combustion chambers. They have no place in T engines as the splash fed oil in the pan will not run UP the valve stem.

That said, some owners of open valve engines in early cars do run seals on the cam tappets to prevent oil escaping down the side of the block and making a mess.

Don't see how they could possibly hurt. Talking strictly about oil consumption here. The intakes could pull vapors through in a closed engine especially with a bit too much stem clearance. As long as they don't interfere with anything, (of course), there shouldn't be a problem using them.

I would not use valve seals. In any engine with splash lubrication, you want as much oil as possible on any moving surface. Valve seals would reduce the amount of oil reaching the valve stem. This would be a very bad thing.

I used to have a lathe that dated from the 1860's with cast iron spindle bearings that was still tight and accurate. Cast iron (the engine block) makes a very good bearing surface due to high amounts of free carbon, as long as it's kept clean and well lubricated. Take away the lubrication and wear sets in quickly. Valve seals prevent oil from getting "up" to the guides..

Valve stem seals are designed to leak a controlled amount. They do not seal off completely. I thought about putting some on my engine when I rebuilt it because the guides are worn and the valve stems are at the maximum. I could not find any that fit the cast nipples where the guides reside. The closest I came were some seals for Harley Davidson motorcycles. So I left them out and I don't seem to have excess oil burning.

Others have used rubber washers and light springs to keep them in place. The only problem I see with that is that they must be allowed to leak a little to keep the guides lubricated. I have come to the conclusion that there is not enough oil in the valve chamber to worry about oil burning from oil climbing up the intake valve stems.

What was the question? seals on a re-build, not a patch up job on a oil burning worn out old engine, putting seals on freshly reamed guides is asking for trouble on a side valve engine. Over head is another story! So answer is still NO!

My original post/question was in connection to a rebuild I'm having done on my 1921. Unfortunately the machinist I'm using has no experience with Model T's and was encouraging the use of valve seals. So I searched the older forum postings for a consensus on the topic and even visited the California Auto Museum in Sacramento hoping for an answer without finding a definite opinion, so I posted here. By the way, the docents who happened to be on site at the time I dropped in at the museum were very friendly and accommodating. They were happy to show me their wonderful Model T exhibit but their T expert wasn't available at the time. They even have a yellow 1913ish touring on display which they allow visitors to sit in and have hands on examinations of. It is a collection of T parts assembled in the spirit of a 1913. A 1926 chassis sits across from the 13. I enjoyed my visit there.

I do have the Model T power plant rebuild booklet but I loaned it to the machinist along with my reprint of the Model T shop manual. My Model T Restoration Handbook by Leslie Henry doesn't comment on valve seals.

So I'll tell my machinist to not adapt valve seals to my engine.

Again, thanks for the comments and explanations. You have all been very helpful.